Aldehydes and ketones are known as important raw materials in fine chemical industry, and are widely applied in industrial chemical production as well as in academic research laboratories. Oxidation is a type of basic and crucial chemical transformation. In industry, aldehydes and ketones are prepared mainly by oxidation. Hence it is promising to develop an economic, mild, eco-friendly and efficient catalytic oxidation method. Traditionally, aldehydes and ketones are prepared by oxidation of corresponding alcohols using at least stoichiometric amount of oxidants. Although this protocol enables the preparation of aldehydes and ketones, however, the use of oxidant such as chromium oxide, manganese oxide and ruthenium oxide etc., would yield almost the same amount of oxidant-derived waste, which causes a serious burden to the environment. Therefore such method is not suitable for large-scale industrial production (Chromium Oxidations in Organic Chemistry; Springer: Berlin, 1984; Regen, S. L.; Koteel, C. J. Am. Chem. Soc. 1977, 99, 3837-3838; Griffith, W. P. Chem. Soc. Rev. 1992, 21, 179-185). Thus much attention has been paid to methods for preparing aldehydes and ketones by catalytic oxidation of corresponding primary or secondary alcohols using oxygen as oxidant with transition metals such as Pd, Ru, Mo—Co, Co, Pt, Os—Cu, Os, Ni, Cu, Fe etc. (Blackburn, T. F.; Schwartz, J. J. Chem. Soc. Chem. Commun. 1977, 157-158; Piera, J.; Backvall, J.-E. Angew. Chem. Int. Ed. 2008, 47, 3506; Sheldon, R. A.; Arends, I. W. C. E.; Brink, G.-J. T.; Dijksman, A. Acc. Chem. Res. 2002, 35, 774; Mallat, T.; Baiker, A. Chem. Rev. 2004, 104, 3037). TEMPO, as a stable oxygen free radical, plays an important role in synergetic catalytic oxidation with Fe or Cu of primary or secondary alcohols to prepare the corresponding aldehydes or ketones.
The present invention overcomes a series of defects of existing technologies such as the use of heavy metals as catalyst, rigorous reaction conditions, time-consuming, limited scope of substrates, high reaction temperature and reaction pressure etc., and thereby provides an efficient method for preparing aldehydes or ketones by aerobic oxidation under atmospheric pressure. In said method, ferric nitrate, TEMPO, and inorganic chlorides are used as co-catalyst, oxygen is used as oxidant, and thereby brings advantages including the reducing chemical wastes, pollutions, cost, and various resources for starting materials, as well as mild reaction conditions and high efficiency. The method according to the present invention is suitable for large-scale industrial production and is eco-friendly.